Acoustic apparatus



June 13, 1933. c, E, LA E 1,913,451

ACOUSTIC APPARATUS Filed July so, 1924 Patented June 13, 1933 UNITEDSTATES PATENT OFFICE CLARENCE E. LANE, 013 MONTCLAIB, NEW JERSEY,ASSIGNOR TO \VESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y.,A CORPGRATION OF NEW YORK ACOUSTIC APPARATUS Application filed July 30,1924. Serial No. 729,009.

This invention relates to acoustic devices, the object being to providea diaphragm which will faithfully and efficiently repro duce soundvibrations throughout the entire range of frequencies of importance inmusic and speech.

In accordance with the general features of the invention there isprovided. an improved form of direct acting conical diaphragm in whichthe dominating modes of vibrations, particularly at the lowerfrequencies, are asymmetrical.

In its preferred embodiment the invention provides a large direct actinghollow acoustic diaphragm having an elliptical periphery, substantiallyfree to vibrate, 'the front and back members of which have conicsurfaces truncated obliquely to their axes so that the conic sectionformed by the conic surface and a cutting plane of either member is anellipse. The members are secured together at their elliptical edges byany suitable means such as cement. In addition the rear member isprovided with an opening whereby suitable actuating means may be mountedwithin the diaphragm in operative relation to the apex of the frontmember. A suitable standard carries a bracket for supporting theactuating device and an annulus "to which the inner edge of the rearmember is secured for supporting the diaphragm.

It is a well known fact that horns and other devices commonly employedin connection with talking machines and loud speaking receivers areinefficient reproducers of acoustic vibrations at low frequencies. Inmany cases, the lower notes appear to be entirely eliminated. It hasbeen found that large diaphragms when properly designed reproduce thelower notes very efficiently. Other things being equal, the larger thediaphragm the lower its fundamental mode of vibration and the samediaphragm when free at its periphery has a lower natural period thanwhen rigidly secured. In this respect diaphragms are analogous to openand closed pipes which for the same dimensions have a lower frequencywhen closed. The diaphragm of the invention is preferably conical inform to permit the use of light materials nance and noticeabledistortion within the audible range. The present invention overcomesthis diiiiculty by providing a diaphragm in which, due to the lack ofsymmetry in the construction, there are substantially no dominatingmodes of vibrations. Particularly is this true in the low frequencyrange where resonance is most noticeable in symmetrical diaphragms.

Referring to the drawing, Fig. 1 is a front view of the loud speakingreceiver embodying the invention, Fig. 2 is a side View, and Fig. 3 isdetail sectional view of the diaphragm.

The front member 5 is a conic surface truncated obliquely to its axis sothat the conic section formed by the cutting plane. is an ellipse.Parchment paper or a good grade of hard drawing paper may be used forthe entire surface or if desired the front member 5 may be made in twosections, 6 and 7, having overlapping edges in which case it ispreferable to make section 6 of a hard surfaced blotting paper and theinsertion 7 of a lighter and stiffer paper such as described above. Thelatter arrangement has been found to extend the range of response toslightly higher frequencies without affecting the low frequency range.

The back member 8 is preferably formed in substantially the same manneras front member 5, but is intersected by a plane at right angles to theaxis of the conic surface to provide an opening in the diaphragm.Members 5 and 8 are secured in opposing relation at their outerperiphery in any suitable manner. As shown tlieelliptical base of themember 5 is slightly larger than that of memher 8 which abuts againstits inner surface and is cemented'thereto. I

A standard 9 carries an annulus 13 to which the inner edge of the member8 may be rigidly attached by any well known means and forms a suitablesupport for the diaphragm. The standard 9 also carries a bracket 12 onwhich is mounted a suitable actuating means 10, connected to the apex ofthe front member 5 by means of a rod 11. As shown the actuating means 10is supported so that the rod 11 has its axis coincident with the axis ofthe front member 5.

A diaphragm constructed in accordance with the invention gives asubstantially smooth response characteristic over the range offrequencies of most important in speech r and music. F or example, adiaphragm hav ing the following proportions will give uni form responseas low as fifty cycles per second: Major axes approximately 3 feet,angle at the apex approximately 148 and the eccentricity of the apexsuch that the ratio of the shortest element to the longest isapproximately 1, to A diaphragm of this size and proportions reproducesthe low notes of a pipe organ with exceptional fidelity withoutsacrificing any of the higher notes. Obviously for ordinary usesdiaphragms as large as this are not required. For a diaphragm of thistype the range of response will be approximately the same as for asymmetrical diaphragm of the same area but the response within thisrange will be much more uniform.

Vhat is claimed is:

1. A large direct acting diaphragm comprising an initially formedconical front member having an eccentric apex and an opposing initiallyformed conical rear member the outer range of which is secured to theouter edge of said front member.

2. A direct acting hollow diaphragm comprising two initially formedconical members having elliptical bases joined together.

3. A direct acting diaphragm comprising an oblique conical front memberhaving an elliptical base and an opposing rear conical member havingbases in planes oblique to each other for supporting said front member.

4:. A direct acting diaphragm comprising a conical member having aneccentric apex and an apertured flexible member having conical surfaceyieldingly supporting said conical member at its periphery and extendinginwardly therefrom.

5. A large direct acting hollow diaphragm one member of which comprisesthe surface of a cone of revolution between its apex and a plane obliqueto its axis.

6. A large direct acting diaphragm comprising a front conical memberhaving an elliptical periphery and a rear conical member comprising thatproportion of a conic surface lying between truncating planes oblique toeach other for supporting said front memher.

7. An acoustic device comprising a diaphragm having a front conicalmember the periphery of which is elliptical and a rear opposingtruncated conical member the smaller and larger bases of which arecircular and elliptical respectively, the elliptical bases of said frontand rear members being secured to gether, means associated with thecircular base for supporting said diaphragm and actuating means carriedby said supporting means operatively associated with said front member.

8. An acoustic device comprising a conical diaphragm having an obliqueconical member, actuated means therefor, and means c0- axial with saidmember for connecting said actuating means thereto.

9. In an acoustic device a direct acting diaphragm comprising an obliqueconical front member having an elliptical base, the length of thelongest element of said front member being approximately 3 times thelength of the shortest element, and an apertured flexible rear membersupporting said front memher at its periphery and extending inwardlytherefrom.

10. In an acoustic device a diaphragm comprising an oblique conicalmember having a vibratile periphery and means supporting said conicalmember whereby its outer edge has various degrees of stifi'ness.

11. In an acoustic device, a large direct acting conical diaphragm,actuating means eccentrically attached thereto, and means supportingsaid actuating means and eccentrically supporting said diaphragm.

12. A hollow acoustic diaphragm comprising two oblique conical membersjoined together at their bases.

13. An acoustic device comprising a diaphragm, means spacedeccentrically from the periphery for supporting said dia hragm, andmeans carried by said support or actuating said diaphragm.

14. A11 acoustic device comprising a conical diaphragm, actuating meanstherefor, and means transmitting vibrations from said actuating means tosaid diaphragm in a direction oblique to the plane of the periphery ofsaid diaphragm.

15. A sound reproducing diaphragm con sisting of a large direct actingsound reproducing diaphragm consisting of a thin sheet of materialhaving an elliptical periphery, means for supporting the periphery ofsaid diaphragm for relatively free vibration, and means for subjectingsaid diaphragm to mechanical vibration substantially at the centerthereof.

16. A sound reproducing diaphragm comprising a large direct acting coneof thin sheet material having an elliptical periphery, means forflexibly supporting the periphery thereof, and means for subjecting saiddiaphragm at its apex to mechanical vibration.

17. In a sound amplifying device, a diaphragm, said diaphragm comprisingan elliptical cone and an elliptical truncated cone surrounding saidelliptical cone, the lesser circumference of said truncated cone and thecircumference of said cone being coincident.

18. An acoustic device comprising a diaphragm having an ellipticalperiphery, a member associated therewith in such manner as to enclose abody of air between it and the diaphragm, and actuating meansoperatively connected with the diaphragm.

19. An acoustic device comprising a diaphragm, the outer edge of whichis elliptical in form and substantially free to vibrate, a memberassociated therewith in such manner as to enclose a body of air betweenit and the diaphragm, and actuating means operatively connected with thediaphragm.

20. An acoustic device comprising a conical diaphragm, the outer edge ofwhich is elliptical in form and substantially free to vibrate, a rearmember associated therewith in such manner as to enclose a body of airbetween it and the diaphragm, and actuating means operatively connectedwith the apex of the diaphragm.

21. An acoustic device comprising a large direct-acting disheddiaphragm, the outer edge of which is elliptical in form and substantially free to vibrate, a member associated therewith in such manneras to enclose a body of air between it and the diaphragm, and actuatingmeans operatively connected with the diaphragm at a portion thereofremoved from its outer edge.

22. An acoustic device comprising a diaphragm having an ellipticalperiphery, means on one side of said diaphragm for actuating it, andmeans connected to the diaphragm periphery and extending away from thedia phragm on the same side of the diaphragm as the first means, saidsecond means defining an air body on said one side of said diaphragm.

23. An acoustic device comprising a vibratory conical member having anelliptical periphery, a hollow member having an elliptical peripheralportion connected to said conical member at its periphery, and meansresponsive to impulses of sound wave frequency connected to the conicalmember.

24. An acoustic device comprising a vibratory conical member having anelliptical periphery, a hollow vibratory member having an ellipticalperipheral portion connected to the conical member at the peripherythereof, and means responsive to impulses of sound wave frequencyconnected to said conical member.

25. An acoustic device comprising a vibratory conical member having anelliptical periphery, a hollow vibratory member having an ellipticalperipheral portion connected to the conical member at the peripherythereof and supporting said conical member and means responsive toimpulses of sound wave frequency connected to said conical member.

26. An acoustic device comprising a directacting vibratory member havinga plurality of portions one of which is a lighter and stiffer materialthan the other and each of which has an elliptical periphery, means forsupporting said member, and means responsive to impulses of sound wavefrequency connected to said member.

27. An acoustic device comprising a hollow vibratory member having aconical and a frusto-conical portion each having elliptical peripheries,and another hollow member supporting said first member, said secondhollow member being connected to the frustoconical portionat theperiphery of the larger base thereof.

In witness whereof, I hereunto subscribe my name this 28th day of JulyA. D. 1924.

CLARENCE E. LANE.

